1. Field of the Invention
This invention relates generally to methods of making magnetic heads, and more particularly to methods of making magnetic heads which protect the P2 pole piece during the ion mill patterning of the yoke.
2. Description of the Related Art
A write head is typically combined with a magnetoresistive (MR) or giant magnetoresistive (GMR) read head to form a read/write recording head, certain elements of which are exposed at an air bearing surface (ABS). The write head is made of first and second pole pieces having first and second pole tips, respectively, which terminate at the ABS. The first and second pole pieces are connected at the back gap, whereas the first and second pole tips are separated by a non-magnetic gap layer. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces, and a coil layer is embedded in this insulation stack. A processing circuit is connected to the coil layer for conducting write current through the coil layer which, in turn, induces write fields in the first and second pole pieces. Thus, write fields of the first and second pole tips at the ABS fringe across the gap layer. In a magnetic disk drive, a magnetic disk is rotated adjacent to, and a short distance from, the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain information in the form of magnetized segments with fields detectable by the read head.
One or more merged heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged head is mounted on a slider that is carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air layer (an “air bearing”) is generated between the rotating disk and the ABS. A force of the air bearing against the air bearing surface is opposed by an opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk.
Improved methods for making magnetic heads have become increasingly important for proper head fabrication and performance. Magnetic head assemblies are typically made of multiple thin film layers which are patterned to form various shaped layers in the head. Some of the layers are electroplated, while other layers are sputter deposited on a wafer substrate.
The conventional method of forming a magnetic pole layer of a magnetic write head involves an electroplating deposition process. Deposition by electroplating, however, limits the choice of materials that can be used for such layers. For high data rate applications, the pole layer material (especially that in the yoke region) should be a highly resistive material or a laminated structure of alternating magnetic and dielectric layers. The yoke region of the pole layer is the region that resides between the pole tip and the back gap. These materials help reduce the eddy current effect and improve the high frequency performance of the write head. This highly resistive or laminated material can be deposited using dry process techniques, such as sputter deposition, where an ion milling process is subsequently used to pattern its shape.
FIG. 1 is the first in a series of illustrations of FIGS. 1–3 which describe the problem of forming the yoke of a magnetic head by ion milling. In FIG. 1 a partially constructed magnetic head 100 is shown; it requires a yoke to be formed thereover to connect the pole pieces together in the back gap region. As partially constructed, magnetic head 100 includes a read sensor 102 formed between first and second shield layers 104 and 106. A first P1 pole piece layer 108 is plated over an insulator layer 107 which is on top of second shield layer 106. A front P1 pedestal 110 is then plated over this first P1 pole piece layer 108 at a contemplated air bearing surface (ABS) line 124, whereas a back gap P1 pedestal 112 is plated over first P1 pole piece layer 108 in the back gap region. First P1 pole piece layer 108, front P1 pedestal 110, and back gap P1 pedestal 112 form the first pole piece of magnetic head 100.
Formed between front and back gap P1 pedestals 110 and 112 are write coils 122 which are on top of and surrounded by an insulator material, such as hard bake resist or alumina (Al2O3). A gap layer 118 is formed over front P1 pedestal 110 and write coils 122. A front P2 pole tip 114 is then formed over gap layer 118 at the ABS line 124, whereas a back gap P2 pedestal 116 is formed over back gap P1 pedestal 112 in the back gap region. Front P2 pole tip 114 and back gap pedestal 116 form the second pole piece of magnetic head 100. An insulator material 120, such as alumina, is formed in between front P2 pole tip 114 and back gap P2 pedestal 116 over gap layer 118 and write coils 122.
In FIG. 2, yoke layer materials 202 are formed over the top surface of front P2 pole tip 114, back gap P2 pedestal 116, and insulator materials 120. Yoke layer materials 202 are made of either highly resistive magnetic materials or a laminated structure made of alternating magnetic and dielectric layers. Such materials are chosen to reduce or break up the effect of eddy currents which otherwise cause a relatively large loss of efficiency, especially at high data rate performance. However, the selection of these materials requires that they be sputter deposited as opposed to, for example, being electroplated. Therefore, due to the full-film sputter deposition of materials, yoke layer materials 202 typically have to be shaped by an ion milling process.
Before ion milling, a photoresist mask 204 is formed over yoke layer materials 202. The front edge of photoresist mask 204 is positioned such that it is recessed away from the ABS line 124 as shown. Photoresist mask 204 is made of a top photoresist layer 206 and a bottom release layer 208. An ion milling process as indicated by arrows 210 is then performed to remove that portion of yoke layer materials 202 that are not covered by photoresist mask 204. However, to guarantee that the uncovered yoke layer materials 202 are sufficiently removed, “over-milling” from between about 10–50% is typically required. Due to the shadowing effect from photoresist mask 204, it takes more time to clean materials at the foot of photoresist mask 204 which increases the total ion milling time.
In FIG. 3, the front portion of the yoke layer materials is shown removed from the ion milling process. A yoke 304 is thereby formed over the front P2 pole tip and the back gap P2 pedestal. Photoresist mask 204 may be removed by dissolving photoresist layer 206 and release layer 208 with a suitable solvent, and conventional head processing may complete the formation of the head. Due to the required over-milling of yoke materials 202, however, a reduced-size or damaged front P2 pole tip 306 is produced as a result. Thus, it is difficult to control the thickness of the P2 pole piece with this process. If utilized in the magnetic head, such a damaged front P2 pole tip 306 will adversely affect the performance of the write head.
Accordingly, what is needed is a method of making a magnetic head which protects the P2 pole piece during the ion mill patterning of the yoke, or other methods which do not reduce the size or damage the P2 pole piece during formation of the yoke.